Street talk refers to the rumors and gossip passed from person to person in the streets and alleys. That's what "street talk" is.
These bits of street talk are stories. The "words" contain power. Actually, it's not power, but stories. There's a saying that spoken words are seeds that take root. People use it when something they talk about often comes true. It shows that words spoken by others have a special power.
A single character can grow into a word, a word can grow into a sentence, a sentence can grow into a paragraph, and a paragraph can grow into a story.
